A02P0261-Engine Power Loss in Flight-Airbus A340-300 B-HXN-Timmins, Ontario-20 October 2002
Safety Action Taken
CFM International (CFM) issued Service Bulletin (SB) 73-0126 (published as CFM56-5C SB 73-0126, dated 13 November 2003). The SB changes the electronic control unit (ECU) software version from C.3.G to C.3.J and ensures that ECU electrical power successfully reverts to aircraft power in the event of a complete or partial permanent magnet alternator (PMA) failure. While this SB applies only to the Airbus A340 and the CFM56-5C engines, all CFM ECU software for the CFM56-5 series will have the improved logic at the next scheduled version release.
In October 2003, Airbus revised the A340 maintenance manual to include specific checks during the removal of the PMA for evidence of rotor/stator contact and radial play of the PMA drive shaft.
Safety Action Required
SB 73-0126 will update the ECU software to ensure that electrical power will successfully revert to aircraft power. This SB applies only to the Airbus A340 aircraft, and, although CFM recommends implementation within six months, the actual timeframe for accomplishing this SB is at the discretion of the operator. Additionally, Airbus advises that it has launched similar initiatives to incorporate software updates on CFM56-5A and -5B engines used on its A319, A320, and A321 family of aircraft. It is anticipated that compliance for these SBs will likewise be at the discretion of the operator. As of November 2004, the total number of aircraft in the Canadian civil aircraft register affected by these SBs approximated 120, most of which are two-engine aircraft.
Given the number of aircraft affected, the known problem with PMA bearing failures, the critical function that the ECU software provides in ensuring engine reliability, and the discretionary nature of the proposed software updates, the Board is concerned that, without regulatory intervention, this known unsafe condition will remain in service well beyond the manufacturer's recommended six-month timeframe for the implementation of SB 73-0126. The Board therefore recommends that:
The Department of Transport ensure the continued airworthiness of Canadian-registered aircraft fitted with the CFM56-5 series engine by developing an appropriate safety assurance strategy to make certain that, in the event of a permanent magnet alternator failure, the electronic control unit will revert to aircraft power. A04-04
Transport Canada's Response:
Through communication with the Canadian aviation industry, Transport Canada has confirmed that all Canadian aircraft presently affected by CFM Service Bulletin 73-0126 will have their ECU software upgraded to version C.3.J by March 2005 therefore; Transport Canada is not planning on taking any further action.
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